this thing, we could generate electricity to light up cities. and sure enough, we do. and we have devices like this. and we put a waterfall over here and turn it, use the energy of that waterfall, potential, kinetic, rotational, mechanical, off it goes this light, huh? do that, or we could put a steam turbine here, direct some expanding steam against the turbine, against the paddle wheel and turn it. and so our civilization really rests on devices like this. but there's gotta be some energy input to be transformed over here. now, here's a neat little thing. when i turn this and i unscrew the lamp, it becomes easier to turn. easier to turn. why? well, when it's unhooked, there's no energy going off. and so what i'm turning against now is a friction. but when it's hooked up, i'm pushing against the friction plus the electricity. so let's--i can show you that. can i have a volunteer? could you come up here, please? what i'm gonna do-- you stand over here, and what i want you to do-- i'm not gonna look, i'm gonna look over here, okay? and i want you to unscrew that, and i'll tell you when it'